Drag reducing device

ABSTRACT

A drag reducing device for a vehicle body having a top wall and a door pivotably mounted to the rear of the body to open toward a side wall of the body, includes a wing sized and configured to turn airflow across the top wall of the body, the wing having a trailing edge and a proximal edge; and an assembly mounted to the door and configured for pivoting the wing so that the trailing edge of the wing is pivoted upward to a position above the top wall of the vehicle body when the door is open and for pivoting the wing so that the trailing edge of the wing is pivoted downward to a position below the top wall of the vehicle body when the door is closed.

REFERENCE TO RELATED APPLICATION

This application is a non-provisional filing of and claims priority toprovisional application No. 62/404,289, filed on Oct. 5, 2016, theentire disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to drag reduction devices for landvehicles, such as trucks, tractor-trailer rigs, vans, buses,recreational vehicles and similar vehicles having a large frontal area.

Fuel economy is a persistent concern for all land vehicles and isparticularly acute for large vehicles such as trucks and tractor-trailerrigs. Fuel economy improvements have been achieved by innovation inengine design and improvements in fuel composition. However, the sizeand shape of the vehicles plays a substantial role in fuel economy.Ultimately, drag is the greatest enemy to fuel economy, with as much as70% of the engine power devoted to cutting through the air in front ofthe vehicle.

Drag is a force that resists the movement of a body through a fluid,whether the body is a baseball and the fluid is air, or the body is aswimmer moving through water. Drag is a function of twocomponents—friction drag and pressure drag. Friction drag is a forcethat acts tangential to a surface of the body. Friction drag isincreased by irregularities or roughness on the surface and decreased bymaking the surface more slippery. A clean truck cuts through the airmore efficiently and with less friction drag than a dirty truck.

Pressure drag is a force that acts perpendicular to a surface and is afunction of the surface area in the direction of travel as well as thevelocity or speed at which the body is traveling. Pressure dragincreases as the square of velocity so that doubling vehicle speedactually creates four times more pressure drag. On the other hand,pressure drag is directly related to surface area so that a ten percentreduction in surface area leads to a ten percent decrease in pressuredrag.

For aerodynamically configured vehicles, such as airplanes, frictiondrag contributes more heavily to overall drag than pressure drag.However, for land vehicles this relationship is reversed significantly.For a typical tractor-trailer, pressure drag can be as much as ten timesgreater than friction drag due to the large frontal surface area of thetruck. Unfortunately, the size of these types of vehicles is dictated bytheir function—hauling products or materials. Unlike passenger vehicles,the box-like shape of trucks cannot be significantly altered. A smallerfrontal surface area means a smaller truck, which means less cargo thatcan be hauled. Pressure drag in land vehicles, and especially in trucks,is increased by pressure “hot spots”, such beneath the undercarriage,behind the rear of the trailer or between the tractor and the trailer.These hot spots are generally regions of low pressure, which causes airflowing over the vehicle to deviate from a streamlined path around thevehicle. Vortices can form in these hot spots that significantlyincrease the pressure drag.

In quantitative terms, if a square body has a drag coefficient (C_(D))of 1.00, elongating the body into a rectangular shape reduces C_(D) to0.80. Adding a rounded nose cuts the coefficient in half to 0.40. Addinga “boat tail” or a conical tail decreases C_(D) further to 0.20. Thetypical boattail configuration includes plates projecting from the rearof the vehicle and angled inwardly at an angle of 10-15°. An ellipticalbody tapered at both ends produces a drag coefficient less than 0.05,but the shape significantly reduces available cargo space and isdifficult to produce.

It has been estimated that a 20% reduction in drag yields at least a 10%increase in fuel economy at highway speeds. For truckers and truckingcompanies, this increase in fuel economy means significantly reducedfuel costs year in and year out. For the environment, increases in fueleconomy mean fewer deleterious emissions. A significant amount of efforthas been expended in developing drag reduction technology for trucks.These efforts include streamlining the tractor, introducing seals, airdeflectors or vortex generators in the gap between the tractor andtrailer, and adding undercarriage skirts, guide vanes, air deflectorsand boat tails to the trailer. Each of these modifications contributesin some measure to the overall drag reduction, so a fully optimized rigwill incorporate a number of these improvements.

Presently, the typical drag reduction device utilizes “mechanical”redirection of the air flow to reduce drag. For instance, one type ofdevice utilizes spoilers or fairings mounted to the top trailing edge ofa vehicle or trailer to redirect the airflow and attempt to reduceturbulence. Another drag reduction device is the boat tail device thatincludes boat tail plates extending rearward from the rear of thetrailer. Boat tail devices can reduce drag by up to ten percent. Thetypical boat tail is a large shell that is mounted over the rear doorsof the trailer. Such devices are cumbersome to install and remove.Moreover, the large unitary shell is difficult to store when access tothe rear doors is desired, such as to unload the trailer.

Other “mechanical” drag reduction devices require intervention by thevehicle operator to deploy and stow the device, while still othermechanical approaches require the vehicle operator to manipulate thedrag reduction device to access the rear doors of the vehicle ortrailer. Some mechanical devices are mounted directly to thevehicle/trailer doors which can eliminate the need to manipulate thedevice in order to access the trailer door. However, these devices arebulky and prevent the trailer/vehicle door from being fully opened flatagainst the side wall of the trailer/vehicle. This discrepancy can posesignificant risks at shipping/receiving locations where trucks arebacked in to closely spaced loading docks. A door that projects too faraway from the side of the trailer can be struck by an adjacent vehicleas it attempts to back into an adjacent loading dock.

Whether the actuator is mechanical or non-mechanical, there is apersistent need for a drag reduction device that does not impede theability to open the rear doors of a trailer or truck on which the deviceis mounted. Moreover, in order to ensure that the drag reduction deviceis consistently used, the device should be “automatic”, meaning that itdoes not require any intervention by the vehicle operator to deploy orto position the device clear of the vehicle/trailer doors when access isdesired for loading or unloading the vehicle. There is also a need for adrag reduction device that has a lower profile when the rear doors areopen than existing devices—i.e., that fits within the space between theopen door and the side of the trailer or vehicle.

SUMMARY

A drag reducing device is provided for a vehicle body having a top walland a door pivotably mounted to the rear of the body to open toward aside wall of the body, that includes a wing sized and configured to turnairflow across the top wall of the body, the wing having a trailing edgeand a proximal edge; and an assembly mounted to the door and configuredfor pivoting the wing so that the trailing edge of the wing is pivotedupward to a position above the top wall of the vehicle body when thedoor is open and for pivoting the wing so that the trailing edge of thewing is pivoted downward to a position below the top wall of the vehiclebody when the door is closed.

In one aspect, the assembly for pivoting the wing includes a mountingplate on which the wing is mounted adjacent the proximal edge of thewing, a base plate mounted to the door below the top wall of the vehiclebody, a pivot plate fastened to the mounting plate and arranged tocontact the vehicle body at the top wall when the door is closed, thepivot plate pivotably connected to the base plate so that the pivotplate is pivotable between a deployed position when the pivot platecontacts the vehicle body and a stowed position when the pivot plate ismoved with the door away from the vehicle body toward the side wall ofthe vehicle body, and a spring member arranged between the base plateand the pivot plate to bias the pivot plate to the stowed position Inthe stowed position the trailing edge of the wing is above the top wallof the vehicle body and in the deployed position the trailing edge ofthe wing is below the top wall of the vehicle body.

In a further aspect, a drag reducing device is provided for a vehiclebody having a side wall and a door pivotably mounted to a door framefixed to the rear of the body to open toward the side wall, thatincludes a side wing assembly pivotably mounted to the door frameadjacent the side wall. The side wing assembly includes a hinge platepivotably mounted to the door frame and extending rearward from the rearof the vehicle body, and a panel pivotably mounted to the hinge plate topivot about a vertical axis relative to the vehicle body, the panelmounted to the hinge plate at a forward edge of the panel and arrangedso that a rear edge of the panel extends rearward from the vehicle bodyin a deployed configuration. At least one first flexible lanyard isconnected between the hinge plate and the door, and at least one secondflexible lanyard connected between the door and the panel adjacent therear edge of the panel.

DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view of the rear of a vehicle or trailer with adrag reduction device mounted thereon.

FIG. 2 is the perspective view shown in FIG. 1, depicted with the dragreduction device in partially exploded view.

FIG. 3 is a side view of the vehicle and device shown in FIG. 2 with therear door closed and the drag reduction device deployed.

FIG. 4 is an end view of the vehicle and device depicted in FIGS. 1-3.

FIG. 5 is a top view of the vehicle and device depicted in FIGS. 1-3.

FIG. 6 is a rear perspective view of a top wing assembly of the dragreduction device shown in the prior figures.

FIG. 7 is a front perspective view of a top wing assembly shown in FIG.6.

FIG. 8 is a rear view of the top wing assembly shown in FIG. 6.

FIG. 9 is a front view of the top wing assembly shown in FIG. 7.

FIG. 10 is a side view of the top wing assembly shown in FIG. 6.

FIG. 11 is an exploded view of the top wing assembly shown in FIG. 6.

FIG. 12 is an exploded view of a spring assembly for the top wingassembly shown in FIG. 11.

FIG. 13 includes several view of the drag reduction device shown in thedeployed position when the rear doors of the vehicle are closed.

FIG. 14 includes several view of the drag reduction device shown in apartially opened position when the rear doors of the vehicle arepartially opened.

FIG. 15 includes several view of the drag reduction device shown in thestowed position when the rear doors of the vehicle are fully opened.

FIG. 16 is a top view of a side wing assembly of the drag reductiondevice depicted in FIG. 1.

FIG. 17 is a side view of the side wing assembly shown in FIG. 16.

FIG. 18 is an exploded view of the side wing assembly shown in FIG. 17.

FIG. 19 is a perspective view of the drag reduction device of thepresent disclosure mounted to a vehicle and in the deployed position.

FIG. 20 is an enlarged view of the deployed drag reduction device viewedfrom the rear of the device.

FIG. 21 is a rear view of the lower tether arrangement for the side wingassembly of the drag reduction device shown in the prior figures.

FIG. 22 is a rear view of the upper tether arrangement for the side wingassembly of the drag reduction device shown in the prior figures.

FIG. 23 is a rear view of the lower tether arrangement for the side wingassembly of the drag reduction device shown in the prior figures, shownwith the rear door partially open.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

According to one embodiment shown in FIGS. 1-5, a drag reducing deviceincludes a pair of top wing assemblies 10, one of each pair mounted to arespective one of the rear doors D of a vehicle V, which may be atrailer, van, semi-trailer and the like. A pair of side wing assemblies100 are also provided, with one each mounted to the rear frame R of thevehicle adjacent to each rear door. As is known in the art, the reardoors D swing outward and toward the side wall S of the vehicle andtypically include some form of latch L at the side wall configured tohold the rear door in the fully open position. The rear door isconfigured so that a narrow gap exists between the side wall S and thedoor D in the fully open and latched position. The side wing assembly100 of the dag reducing device of the present disclosure is configuredto nestle within that narrow gap without interfering with the ability ofthe rear door to be fully opened and latched. As noted in FIGS. 3 and 5,the top wing assemblies are configured to extend about 12.0 inches fromthe rear of the top wall T of the vehicle. The side wing assemblies areconfigured to extend 20-21 inches from the rear doors. All of the wingassemblies are configured to direct airflow at the rear of the vehicleto reduce drag. It has been found that these dimensions of thecomponents of the drag reducing device provide optimal drag reduction;however, other dimensions for the components may be contemplated. Asdepicted in FIG. 1, the top wing assemblies overlap the top edges of theside wing assemblies and are preferably arranged substantially flushwith the side wing assemblies when the drag reducing device is in itsdeployed configuration as shown in FIGS. 1-5.

The top wing assemblies 10 include a left wing 11 and a right wing 12,with each wing mounted to a corresponding left and right rear door. Thewing assemblies integrate with a gutter foil 15 that is affixed to thetop wall T of the vehicle. A single gutter foil is depicted in FIGS.1-2, but a multi-piece gutter foil is contemplated for use with the topwings 11, 12. The left and right wings 11, 12 are configured to directlyabut or slightly overlap the gutter foil in the deployed position toprovide a smooth transition for air flow over the top rear of thevehicle. Each wing assembly includes a spring assembly 20 that pivotsthe wing assemblies from their deployed position to a stowed position,as described herein.

Referring to FIGS. 6-12, details of a top wing assembly 10 areillustrated. Each wing 11 and 12 is supported by a pivot assembly 21,and in particular is fastened adjacent its forward edge 11 b, 12 b to acorresponding wing mount 24 that is in turn fastened to a flange 26 of apivot plate 22 by fasteners 25. The wing mount 24 is provided withmounting holes 27 to receive fasteners to affix the wing to the mount.As shown in detail in FIG. 11, the pivot assembly 21 further includes acollar 28 that is configured to receive a pivot rod 29 so that the pivotplate 22 can pivot freely about the rod. The pivot rod 29 also passesthrough holes 31 in a bottom link 30. The pivot rod is held in placeextending through the collar and bottom link by retaining rings 29 asnapped onto the ends of the rod in a conventional fashion.

The bottom link 30 is U-shaped, as shown in FIG. 11 to fit around thecollar 28 of the pivot plate 22. The pivot rod 29 extends through theholes 31 in the lower portion of the U-shaped link 30, while anintermediate shaft 33 extends through holes 32 in an upper portion ofthe link 30. The intermediate shaft also extends through holes 34 a inpivot posts 34 and through holes 36 in a lower portion of a mid link 35.The bottom link 30 sits between the two pivot posts 34 while the midlink 35 is U-shaped to fit around the two pivot posts 34. Theintermediate shaft 33 is held at its ends by retaining rings, similar tothe retaining rings 29 a, so that the two links 30, 35 can pivotrelative to each other and relative to the pivot posts 34. The pivotposts 34 are spring biased to exert an upward force on the bottom linkand mid link, as described further herein.

The mid link 35 receives an upper rod 40 that extends through holes 37in the upper portion of the link. The upper rod 40 is sized to passthrough holes 43 in the upper rear portion of a pair of tri-axle links42 that flank the bottom link 30 and mid link 35. Again, the upper rodis held in position by retaining rings at the ends of the rod so thatthe tri-axle links and mid link can pivot relative to each other. Thetri-axle links are pivotably mounted to a base plate 50 by a pivot rod46 passing through pivot holes 45 at the lower portion of the links 42.The pivot rod 46 also passes through a pair of collars 47 on the baseplate 50, with the collars 47 configured to sit within the U-shapedtri-axle links 42.

The tri-axle-links 42 receive an upper rod 49 through holes 48 in theupper forward portion of the links. The upper rod 49 also passes throughcollars 51 (FIGS. 9, 10) in the upper portion of the pivot plate 22beneath the flange 26. The pivot assembly 21 is thus operable in theform of a four-bar linkage to exert a pivot force on the wing mount 24based on an upward force applied through the pivot posts 34. Thislinkage movement manifests itself in shifting the position of the wingmount 24, and thus the top wings 11, 12 mounted thereto, from thedeployed position shown in FIG. 13, to a stowed position, shown in FIG.15. In particular, in the deployed position, the wing 11 is angleddownward relative to the top wall T of the vehicle so that the trailingedge 11 ais below the level of the top wall. On the other hand, in thestowed position, the wing 11 must be tilted upward so that the trailingedge 11 a can slide over the top wall T, as shown in FIG. 15. The pivotassembly 21 is thus configured so that as the rear door D is opened thewing 11 starts to pivot upward, to an intermediate position as shown inFIG. 14B, until it reaches its stowed angle that allows the trailingedge 11 ato clear the top wall T of the vehicle.

The upward force applied through the pivot posts 34 is generated by thespring assembly 20. Turning to FIG. 12, the spring assembly 20 ismounted within the base plate 50, which is in turn mounted at the top ofthe rear door D, since it is ultimately supporting the top wingassemblies to be aligned with the top wall T of the vehicle. The upperportions of the pivot posts 34 extend through bores 66 in a top flangeof the base plate 50. Retaining rings 62 limit the range of upwardmovement of the posts through the bores. The lower portions 52 of thepivot posts 34 extend through corresponding compression springs 54. Thesprings 54 are seated on a pre-load plate 56 that is affixed to thebottom of the base plate 50. Each spring bears against a correspondingspring washer 61 that bears against a retaining ring 60 mounted on thelower portion 52 of the pivot post 34. The springs are initiallycompressed to apply a biasing upward force to the pivot posts.Adjustment bolts 58 can adjust the amount of spring force or pre-loadapplied by the springs 54 by adjusting the position of the pre-loadplate 56 relative to the base plate.

When the top wing assembly is in its deployed position the rear door isclosed at the rear of the vehicle. The edge 26 a of the upper flange 26contacts the fixed frame R surrounding the door thereby pushing thepivot plate 22 outward away from the vehicle. The pivot assembly 21controls the movement of the pivot plate so that the plate pivots aboutthe pivot rod 29 to thereby pivot the associated wing 11, 12 downward tothe deployed position shown in FIG. 13. This movement also provides adownward force on the pivot posts 34 which in turn applies a compressionforce to the springs 54 by way of the spring washers 61. The springforce keeps the wing assemblies held tightly in the deployed positioneven under buffeting and road vibration. The stored energy in the springis released when the rear door is opened and the pivot plate 22 is nolonger in contact with the vehicle body. The springs then provide theupward force on the bottom link 30 and mid link 35 to pivot the wing toits stowed position described above.

In the event that the spring assembly 20 and/or pivot assembly 12 isjammed, such as due to ice or debris interfering with the components, amanual override assembly 70 is provided, as shown in FIG. 2, that allowsthe operator to apply an upward force to the pivot posts 34 to pivot thewing assemblies to their upward tilted stowed positions. As shown inFIGS. 21-22, the override assembly 70 includes a lanyard rail 72 thatdefines a channel 73 extending vertically up the rear door D. A pushplate 74 is seated within the channel 73 and is provided with a handle75 at the bottom of the push plate. The operator manually pushes thehandle 75 upward to move the push plate upward into contact with thepre-load plate 56. This upward force pushes the pre-load plate into thesprings, which in turn push against the pivot posts to manually forcethe linkage movements to pivot the wings upward. The handle 77 may beprovided with an angled surface 76 that can be contacted by the outeredge of the side wing assembly as the rear door opens.

Turning now to FIGS. 16-18, details of the side wing assemblies 100 areshown. The side wing assemblies each include a panel 102 that may beformed of a composite material. In one embodiment, the panel isgenerally planar, at least in the stowed position so that the panel canfit neatly in the gap between the opened rear door D and the side wall Sof the vehicle. The panel 102 may be configured to bend or bow when inthe deployed position. As shown in FIG. 1, the panels 102 are sized toextend substantially along the entire height of the rear door and mayeven be configured to extend slightly below the door provided it doesnot interfere with the vehicle lights. An edge plate 104 is affixed tothe outboard vertical edge of the panel 102 and may be configured with acurvature for improved aerodynamic efficiency of the side wing assembly100. The inboard vertical edge of the panel 102 is mated to a hingeplate 106 that defines a vertical hinge pocket 107. The hinge pocketreceives a hinge rib 111 of a knuckle panel 110. The hinge plate 106further includes a hinge plate panel 108 that overlaps the knuckle panel110. Magnets 112 between the hinge plate panel 108 and the knuckle panel110 can help hold the panels in their deployed positions shown in FIG.13.

As illustrated in FIG. 16, the knuckle panel 110 includes its ownvertical hinge pocket 113 that receives a hinge rib 116 of a 180° hingeassembly 115. The 180° hinge assembly 115 includes a hinge 117 and abase plate 118 that is affixed to the rear door frame R of the vehicle,as shown in FIG. 20. The hinge assembly 115 can thus pivot 180° from thedeployed position shown in FIG. 16 in which the hinge overlaps the baseplate 118 to a stowed position in which the hinge is complete open withthe hinge rib 116 disposed against the side wall S of the vehicle body.In this position, the hinge rib 111 of the panel 102 allows the panel topivot to a stowed position generally parallel to the side wall of thevehicle body and overlapping the hinge plate panel 118 and hingeassembly 115.

As shown in FIGS. 21-23, the side wing assemblies are tethered to therear door by lanyards 120, 122. The lanyards 120 are connected at oneend to the edge plate 104 and at their inboard end to the lanyard rail72. The lanyards 122 are connected at one end to the hinge plate 107 orto an inboard edge of the panel 102. The lanyards 120, 122 hold the sidewing assemblies in their deployed positions as the vehicle is traveling.It is understood that the air flow and air pressures at the rear of thevehicle body automatically cause the composite panel 102 to assume itsdrag reducing configuration extending rearward from the rear of thevehicle and angled slightly inward relative to the side wall of thevehicle. The lanyards thus prevent the composite panel 102 from pivotingtoo far outward relative to the side of the vehicle, thereby diminishingthe drag reduction performance of the side wing assembly 100.

The edge lanyards 120 can help impart an airfoil curvature to the panel102 as the air flows over the side wing assemblies. The edge lanyards120 are also sized to hold the panel 102 at a desirable angle of attackrelative to the side wall S of the vehicle. In one embodiment, thepanels 102 are angled inwardly from the side walls at an angle of about14° to provide optimum aerodynamic performance. Other angles may becontemplated. The lanyards 120 are mounted within a channel 77 in thelanyard rail and may be vertically adjustable to adjust the angle of theside wing assembly.

The present disclosure should be considered as illustrative and notrestrictive in character. It is understood that only certain embodimentshave been presented and that all changes, modifications and furtherapplications that come within the spirit of the disclosure are desiredto be protected.

For instance, the spring assembly 20 may incorporate componentsexhibiting spring-type behavior other than the compression springs 54.For instance, the spring assembly can incorporate a pneumatic orhydraulic cylinder capable of generating the force to pivot the pivotplate 22, and ultimately the wings 11, 12 as described above.

Furthermore, the pivot plate 22 can be mounted directly on the rear doorD rather than indirectly mounted on the door through the base plate 50.The spring assembly 20 can also be mounted on the rear door, such as bya flange arrangement separate from the base plate.

What is claimed is:
 1. A drag reducing device for a vehicle body having a top wall and a door pivotably mounted to the rear of the body to open toward a side wall of the body, the device comprising: a wing sized and configured to turn airflow across the top wall of the body, the wing having a trailing edge and a proximal edge; a base plate mounted to the door below the top wall of the vehicle body; an assembly for pivoting the wing so that said wing is pivoted upward from a deployed position in which the trailing edge is below the top wall of the vehicle body to a stowed position in which the trailing edge is above the top wall of the vehicle body, the spring assembly including; a mounting plate on which said wing is mounted adjacent the proximal edge of said wing; a pivot plate fastened to said mounting plate and arranged to contact the vehicle body when the door is closed, said pivot plate pivotably connected to the door so that said pivot plate is pivotable between a first position in which the pivot plate contacts the vehicle body corresponding to the deployed position of said wing, an intermediate position in which the pivot plate is moved with the door away from the vehicle body toward the side wall of the vehicle body and a second position corresponding to said stowed position of said wing; and a spring member arranged between said base plate and said pivot plate to bias the pivot plate to the second position.
 2. The drag reducing device of claim 1, wherein said pivot plate is pivotably mounted to said base plate.
 3. The drag reducing device of claim 2, wherein said assembly for pivoting the wing further includes a linkage assembly connecting said pivot plate to said base plate.
 4. The drag reducing device of claim 2, wherein: said assembly for pivoting the wing further includes; at least one elongated post slidably supported by said base plate; a pre-load plate fastened to said base plate; a spring washer fastened to said each of at least one elongated post; and said spring member is a spring concentrically disposed around each of said at least one elongated post between said pre-load plate and said spring washer, said spring being initially compressed to apply a biasing upward force to each of said at least one elongated post; and said pivot plate is connected to said at least one elongated post by said linkage assembly, said linkage assembly configured to convert upward movement of said at least one elongated post under force of said spring to pivoting movement of said pivot plate.
 5. The drag reducing device of claim 4, wherein said pre-load plate is adjustably fastened to said base plate to adjust the biasing upward force exerted by the spring on each of said at least one elongated post.
 6. The drag reducing device of claim 4, wherein said assembly for pivoting the wing includes two elongated posts with a corresponding spring concentrically disposed thereon.
 7. The drag reducing device of claim 1, further comprising a manual override operable to pivot said wing to said stowed position after a failure of said spring member, said manual override including a push rod slidably mounted to the door and arranged to push the pre-load plate upward.
 8. The drag reducing device of claim 7, wherein said manual override further includes: an elongated track fastened to the door below said base plate; said push rod slidably disposed within said track with an upper end of said push rod adjacent said pre-load plate, said push rod having a first position in which said upper end of said push rod is not in contact with said pre-load plate and slidable within said track to a second position in which said push rod pushes said pre-load plate upward, thereby pushing said at least one elongated post upward; and a handle fastened to a lower end of said push rod for manual activation of said push rod.
 9. A drag reducing device for a vehicle body having a top wall and a door pivotably mounted to the rear of the body to open toward a side wall of the body, the device comprising: a wing sized and configured to turn airflow across the top wall of the body, the wing having a trailing edge and a proximal edge; an assembly mounted to the door and configured for pivoting the wing so that the trailing edge of said wing is pivoted upward to a position above the top wall of the vehicle body when the door is open and for pivoting the wing so that the trailing edge of said wing is pivoted downward to a position below the top wall of the vehicle body when the door is closed. 